Olive Branch is an unincorporated census-designated place in Alexander County, Illinois, United States. Although it is unincorporated, it has a post office, with the ZIP code of 62969. Its population was 864 at the 2010 census.Olive Branch is part of the Cape Girardeau–Jackson, MO-IL Metropolitan Statistical Area.Olive Branch is located at 37°10′07″N 89°21′06″W / 37.16861°N 89.35167°W / 37.16861; -89.35167.As of the census of 2000, there were 879 people, 389 households, and 314 families residing in the ZCTA. There were 505 housing units. The racial makeup of the ZCTA was 97.38% White, 1.02% Black or African American, 0.46% Native American, 0.11% Pacific Islander, 0.23% from other races, and 0.80% from two or more races. Hispanic or Latino of any race were 0.23% of the population.There were 878 households out of which 26.7% had children under the age of 18 living with them, 56.0% were married couples living together, 7.2% had a female householder with no husband present, and 32.